Facebook Open Graph Error - Inferred Property

You need a space after the final set of quote marks

<meta property="og:url" content="http://www.mywebaddress.com"/>

Should be..likes this one

<meta property="og:url" content="http://www.mywebaddress.com" />

Are those tags on 'http://www.mywebaddress.com'?

Bear in mind the linter will follow the og:url tag as this tag should point to the canonical URL of the piece of content - so if you have a page, e.g. 'http://mywebaddress.com/article1' with an og:url tag pointing to 'http://mywebaddress.com', Facebook will go there and read the tags there also.

Failing that, the most common reason i've seen for seemingly correct tags not being detected by the linter is user-agent detection returning different content to Facebook's crawler than the content you're seeing when you manually check